Inkjet printers eject drops of ink through an array of nozzles to effect printing on a media substrate. The nozzles are typically formed on a silicon wafer substrate using semiconductor fabrication techniques. Each nozzle is a MEMS (micro electro-mechanical systems) device driven by associated drive circuitry formed on the same silicon wafer substrate. The MEMS nozzle devices and associated drive circuitry formed on a single nozzle is commonly referred to as a printhead integrated circuit (IC).
Some inkjet printheads have a single printhead IC. These are scanning type printheads that traverse back and forth across the width of a page as the printer indexes the length of the page past the printhead. The Applicant has developed a range of pagewidth printheads that have a nozzle array as long as the printing width of the page. These printheads remain stationary in the printer as the page is fed past. This allows much higher print speeds but is more complicated in terms of controlling the operation of a much larger array of nozzles.
Inkjet printers can use a variety of techniques to eject ink from the nozzle. Usually, each nozzle has its own actuator mechanism and within these types of printer, the thermal actuator or BubbleJet™ (Bubblejet is a trademark of Canon K.K.). These have a small heater element associated with each nozzle that superheats the ink for form a vapor bubble. The vapor bubble creates pressure pulse in the ink that ejects a drop through the nozzle.
During periods of inactivity, water can evaporate from the ink in the nozzles. This increases the viscosity of the ink to the point where the bubble is unable to eject the drop. The nozzle becomes clogged and inoperable.
Many printers have a printhead maintenance regime that can recover clogged nozzles and clean the exterior face of the printhead. These create a vacuum to suck the ink through the nozzle so that the less viscous ink refills the nozzle. A relatively large volume of ink is wasted by this process requiring the cartridges to be replaced more frequently.